283 



mosaic disease, or yellow leaf blight, is quite characteristic of 

 the early stages of the trouble as it is here delined, and ren- 

 ders it possible to differentiate it readily from the other 

 troubles, which are often spoken of as " black rust," but 

 which are in reality quite different in their nature. The term 

 "yellow leaf blight" was first used by the author in 1892* 

 '• M3saic disease" was added to this term or used synonym- 

 ously, a few months later.f The latter seems the more ap- 

 propriate, but since the former was first used in differentiating 

 this peculiar disease from the others, it seems well at least to 

 continue its use in the literature of the subject for the present. 

 During very rapid progress of the disease also the mosaic 

 character of the leaf is not so apparent as during the normal 

 development. 



" In 1891 a preliminary investigation of the so-called black 

 rust was made. I The study was confined entirely to the or- 

 ganisms present on the leaf and other parts of the plant, and 

 it was not possible at that time to do more than to record the 

 presence of certain fungus organisms, to observe their botan- 

 ical characters, and to note the fact that their presence at 

 least hastened the destruction of the plant. 



" The following year investigations taken up at the begin- 

 ning of the season confirmed the view that the organisms 

 hastened the destruction of the plant, and at the same time 

 demonstrated the fact that the organisms did not initiate the 

 disease but only aggravated it. 



" The results of the trials of Bordeaux mixture, eau celeste, 

 and copper sulphate indicated that this disease could not be 

 prevented by the application of fungicides, and cotfiimed the 

 conclusion, drawn from observations of a different character, 

 that it was due to physiological causes. 



" Experiments conducted under the direction of the author 

 in several localities in Alabama during two seasons showed a 

 considerable reduction of the disease on plats where kainit 

 was the fertilizer used. 



" At Auburn an experiment was conducted on three plats. 

 Plat No. 1, on which cow peas had been grown, received before 

 plowing a heavy dressing of kainit and acid phosphate. No 

 nitrogenous fertilizer was applied. Plat No. 2 received nitrate 

 of soda in addition to other fertilizers, but no kainit. Plat 

 No. 3 received a complete fertilizer. In July there was a per- 

 ceptible yellowing of the plants in plat 1, while plats 2 and 3 



♦Alabama College Sta. Bui. 36. 

 t Alabama College Sta. Bui. 41. 

 t Alabama College Sta. Bui, 27; Bot. Gaz , 16 (1891; No. 3, pp. 61-65. 



